US20190094446A1

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Publication number: US20190094446A1
Application number: US16/126,538
Authority: US
Inventors: Seulgi KIM; Yongkyu KANG; Sangchul Byun; Kangwoo LEE
Original assignee: Samsung Display Co Ltd
Current assignee: Samsung Display Co Ltd
Priority date: 2017-09-25
Filing date: 2018-09-10
Publication date: 2019-03-28
Also published as: KR20190035974A

Abstract

A backlight unit includes: a light source; and a light guide plate including: an upper surface facing a display panel, a lower surface opposing the upper surface, including: a prism pattern area provided in plurality, and a linear pattern area provided between prism pattern areas, and a light incident surface facing the light source. The prism pattern area includes a prism provided in plurality arranged along a first direction perpendicular to the light incident surface, the linear pattern area comprises a linear pattern provided in plurality arranged along a second direction parallel to the light incident surface, and within the prism pattern area, a length of each of the prisms extends in the second direction parallel to the light incident surface, and lengths of the prisms increase as a distance along the first direction from the light incident surface increases.

Description

This application claims priority to Korean Patent Application No. 10-2017-0123103, filed on Sep. 25, 2017, and all the benefits accruing therefrom under 35 U.S.C. §119, the contents of which is incorporated by reference herein in its entirety.

BACKGROUND1. Field

Embodiments of the invention relate to a backlight unit and a display device. More particularly, embodiments of the invention relate to a backlight unit and a display device having relatively high luminous efficiency by improving light incident to a light guide plate from a light source that may otherwise leaks toward a side surface of the light guide plate without being emitted perpendicularly from the light guide plate and/or to a display panel of the display device.

2. Description of the Related Art

Liquid crystal display (“LCD”) devices are a type of flat panel display (“FPD”) devices which have found wide application thereof. The LCD device includes two substrates including field-generating electrodes, e.g., a pixel electrode and a common electrode, and a liquid crystal layer interposed therebetween. Upon applying voltage to the field-generating electrodes, liquid crystal molecules of the liquid crystal layer are rearranged such that an amount of transmitted light is controlled in the LCD device.

An LCD device, which is a passive display device, includes a display panel which displays images with light and a backlight unit (“BLU”) which generates light and provides the light to the display panel. Backlight units are classified into a direct type backlight unit, an edge type backlight unit and a corner type backlight unit according to the position of the light source.

Edge type backlight units are widely used since manufacturing thereof is relatively easy, weight is relatively light and power consumption thereof is relatively low power as compared to direct type backlight units. In the case of the edge type backlight unit, a plurality of optical sheets for diffusing and collimating light provided from the light source may be disposed between a light guide plate and a display panel within the display device.

SUMMARY

Embodiments of the invention may be directed to a backlight unit and a display device having relatively high luminous efficiency by reducing a light incident to a light guide plate from a light source that leaks toward a side surface of the light guide plate without being emitted perpendicularly therefrom such as towards a display panel.

According to an exemplary embodiment, a backlight unit includes: a light source which generates light used by a display panel to display an image; and a light guide plate which guides the light from the light source towards the display panel, the light guide plate including: an upper surface facing the display panel, a lower surface opposing the upper surface, including: a prism pattern area provided in plurality, and a linear pattern area provided between prism pattern areas, and a light incident surface facing the light source. The prism pattern area includes a prism provided in plurality arranged along a first direction perpendicular to the light incident surface, the linear pattern area includes a linear pattern provided in plurality arranged along a second direction parallel to the light incident surface, and within the prism pattern area, a length of each of the prisms extends in the second direction parallel to the light incident surface, and lengths of the prisms increase as a distance along the first direction from the light incident surface increases.

Each of the linear patterns may have at least one of triangular, semicircular, semi-elliptical, circular and trapezoidal cross-sectional shape.

Each of the linear patterns may have at least one of an embossed shape and a depressed engraved shape.

Each of the linear patterns may have a width in a range from about 5 micrometers (μm) to about 500 μm in the second direction.

The light guide plate may further include a body portion having a lower surface common to each of the prisms and the linear patterns. A first inclined surface of each of the linear pattern may have an angle in a range from about 1 degree to about 80 degrees with respect to the lower surface of the body portion.

The plurality of linear patterns may be disposed directly adjacent to and parallel to each other.

The plurality of linear patterns may be spaced apart from each other.

Linear patterns adjacent to each other may be arranged at an angle in a range from about 0 degrees to about 60 degrees with respect to each other.

Each the plurality of linear patterns may have a length extending in the first direction perpendicular to the light incident surface.

Lengths of the linear patterns may be substantially equal to each other.

The linear patterns may have different lengths from each other.

Lengths of the plurality of linear patterns may increase as a distance from a center portion of the linear pattern area decreases in the second direction.

Ends of each of the linear patterns may be aligned with the light incident surface.

The light guide plate may further include a light opposing surface opposing the light incident surface along the first direction perpendicular to the light incident surface. Each of the linear patterns may be aligned with the light opposing surface.

The plurality of prisms may be disposed directly adjacent to and parallel to each other in the second direction.

Each of the prisms may have at least one of an embossed shape and a depressed engraved shape.

The light guide plate may further include a body portion having a lower surface common to each of the prisms and the linear patterns. An angle between a first inclined surface of each of the prisms and the lower surface of the body portion may be substantially equal to an angle between a second inclined surface of each of the prisms and the lower surface of the body portion.

The upper surface of the light guide plate may include a plurality of lens patterns.

According to an exemplary embodiment, a display device includes: a display panel which displays an image with light; a light source which generates the light; and a light guide plate which guides the light from the light source towards the display panel, the light guide plate including: an upper surface facing the display panel, a lower surface opposing the upper surface, including: a prism pattern area provided in plurality, and a linear pattern area provided between prism pattern areas, and a light incident surface facing the light source. The prism pattern area includes a prism provided in plurality arranged along a first direction perpendicular to the light incident surface, the linear pattern area includes a linear pattern provided in plurality arranged along a second direction parallel to the light incident surface, within the prism pattern area, a length of each of the prisms extends in the second direction parallel to the light incident surface, and lengths of each of the prisms increase as a distance along the first direction from the light incident surface increases, within the linear pattern area between prism pattern areas, the plurality of linear patterns are spaced apart from each other along the second direction, and within a plane defined by the first and second directions, each of adjacent linear patterns spaced apart from each other is disposed inclined with respect to the light incident surface of the light guide plate.

With respect to the light incident surface of the light guide plate, a first linear pattern forms a first angle and a second linear pattern forms a second angle, the first linear pattern forming the first angle alternates in the second direction with the second linear pattern forming the second angle, and the first and second linear patterns form.

The foregoing is illustrative only and is not intended to be in any way limiting. In addition to the illustrative exemplary embodiments and features described above, further exemplary embodiments and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the accompanying drawings, where:

FIG. 1 is an exploded perspective view illustrating an exemplary embodiment of a display device according to the invention;

FIG. 2 is a perspective view illustrating an exemplary embodiment of a light guide plate and a light source member of a display device according to the invention;

FIG. 3 is an enlarged perspective view illustrating area “A” ofFIG. 2;

FIG. 4 is a perspective view illustrating another exemplary embodiment of a light guide plate and a light source member of a display device according to the invention;

FIG. 5 is an enlarged perspective view illustrating area “B” ofFIG. 4;

FIG. 6 is an enlarged perspective view illustrating area “C” ofFIG. 5;

FIG. 7 is a cross-sectional view taken along line I-I′ ofFIG. 6;

FIGS. 8aand 8bare perspective views illustrating an exemplary embodiment of a plurality of prisms and a plurality of linear patterns arranged at a light guide plate according to the invention;

FIG. 9 is a perspective view illustrating another exemplary embodiment of a plurality of prisms and a plurality of linear patterns arranged at a light guide plate according to the invention;

FIG. 10 is a perspective view illustrating still another exemplary embodiment of a plurality of prisms and a plurality of linear patterns arranged at a light guide plate according to the invention;

FIG. 11 is a perspective view illustrating yet another exemplary embodiment of a plurality of prisms and a plurality of linear patterns arranged at a light guide plate according to the invention;

FIG. 12 is a perspective view illustrating yet another exemplary embodiment of a plurality of prisms and a plurality of linear patterns arranged at a light guide plate according to the invention; and

FIG. 13 is a perspective view illustrating yet another exemplary embodiment of a plurality of prisms and a plurality of linear patterns arranged at a light guide plate according to the invention.

DETAILED DESCRIPTION

Exemplary embodiments will now be described more fully hereinafter with reference to the accompanying drawings. Although the invention may be modified in various manners and have several exemplary embodiments, exemplary embodiments are illustrated in the accompanying drawings and will be mainly described in the specification. However, the scope of the invention is not limited to the exemplary embodiments and should be construed as including all the changes, equivalents and substitutions included in the spirit and scope of the invention.

In the drawings, thicknesses of a plurality of layers and areas are illustrated in an enlarged manner for clarity and ease of description thereof. When a layer, area, or plate is referred to as being related to another element such as being “on” another layer, area, or plate, it may be directly on the other layer, area, or plate, or intervening layers, areas, or plates may be present therebetween. Conversely, when a layer, area, or plate is referred to as being related to another element such as being “directly on” another layer, area, or plate, intervening layers, areas, or plates may be absent therebetween. Further when a layer, area, or plate is referred to as being related to another element such as being “below” another layer, area, or plate, it may be directly below the other layer, area, or plate, or intervening layers, areas, or plates may be present therebetween. Conversely, when a layer, area, or plate is referred to as being related to another element such as being “directly below” another layer, area, or plate, intervening layers, areas, or plates may be absent therebetween.

The spatially relative terms “below,” “beneath,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe the relations between one element or component and another element or component as illustrated in the drawings. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation, in addition to the orientation depicted in the drawings. For example, in the case where a device illustrated in the drawing is turned over, the device positioned “below” or “beneath” another device may be placed “above” another device. Accordingly, the illustrative term “below” may include both the lower and upper positions. The device may also be oriented in the other direction and thus the spatially relative terms may be interpreted differently depending on the orientations.

Throughout the specification, when an element is referred to as being “connected” to another element, the element may be physically and/or electrically connected to the other element.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms, including “at least one,” unless the content clearly indicates otherwise. “At least one” is not to be construed as limiting “a” or “an.” “Or” means “and/or.” As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms “comprises,” “including,” “includes” and/or “including,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof

It will be understood that, although the terms “first,” “second,” “third,” and the like may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. Thus, “a first element” discussed below could be termed “a second element” or “a third element,” and “a second element” and “a third element” may be termed likewise without departing from the teachings herein.

“About” or “approximately” as used herein is inclusive of the stated value and means within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art, considering the measurement in question and the error associated with measurement of the particular quantity (i.e., the limitations of the measurement system). For example, “about” may mean within one or more standard deviations, or within ±30%, 20%, 10%, 5% of the stated value.

Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by those skilled in the art to which this invention pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an ideal or excessively formal sense unless clearly defined in the present specification.

Exemplary embodiments are described herein with reference to cross section illustrations that are schematic illustrations of idealized embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments described herein should not be construed as limited to the particular shapes of regions as illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, a region illustrated or described as flat may, typically, have rough and/or nonlinear features. Moreover, sharp angles that are illustrated may be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the present claims.

Some of the parts which are not associated with the description may not be provided in order to specifically describe embodiments of the invention and like reference numerals refer to like elements throughout the specification.

A passive display device includes a display panel which generates and displays images with light, and a backlight unit (“BLU”) which generates the light and provides the light to the display panel. A plurality of optical sheets for diffusing and collimating light provided from the light source may be disposed between a light guide plate of the backlight unit and a display panel of the display device.

In accordance with reducing a total thickness of the passive display device, omitting the plurality of optical sheets between the light guide plate and the display panel has been researched. As such an attempt, research has been carried out to arrange a pattern for perpendicularly emitting a light from a light source to be incident to the light guide plate. However, a portion of the light incident to the light guide plate from the light source undesirably leaks toward a side surface of the light guide plate without being emitted perpendicularly therefrom such as toward the display panel, and thus luminous efficiency is degraded.

In this specification, the display device is described as being a liquid crystal display (“LCD”) device. However, exemplary embodiments are not limited thereto, and any display device that receives light such as from a backlight unit and displays images with the received light may be included in the scope of the invention.

FIG. 1 is an exploded perspective view illustrating an exemplary embodiment of an LCD device according to the invention.

Referring toFIG. 1, a display device according to an exemplary embodiment includes anupper frame110, adisplay panel120, anintermediate frame130, a light source (member)portion140, alight guide plate150, areflection sheet160 and alower frame170.

Hereinafter, theintermediate frame130, thelight source member140, thelight guide plate150, thereflection sheet160, thelower frame170, or the like are collectively called a backlight unit. The backlight unit generates light and provides the light to thedisplay panel120 for displaying an image.

Theupper frame110 has an opening window for exposing an active area of thedisplay panel120 to outside the display device. Theupper frame110 is disposed so as to cover an edge of a front surface and a side surface of thedisplay panel120. Theupper frame110 may include a relatively rigid metal material such as stainless steel and/or a material having relatively good heat dissipation properties such as aluminum or an aluminum alloy.

Thedisplay panel120 may be provided in a quadrangular plate shape. Thedisplay panel120 may receive an electric signal and light from the outside thereof, and display images with the light. Thedisplay panel120 may include a first (display)substrate121, asecond substrate123 opposing thefirst substrate121, an light controlling layer such as a liquid crystal layer (not illustrated) between thefirst substrate121 and thesecond substrate123, or the like.

Thefirst substrate121 includes therein a pixel electrode provided in plurality arranged in a matrix, a switching element such as a thin film transistor with which a driving voltage is applied to each of the pixel electrodes and various (conductive) signal lines through which control, driving and/or power signals are applied for driving the pixel electrodes and the thin film transistor to display an image. These elements may be disposed on a base substrate within thefirst substrate121.

Thesecond substrate123 is disposed to oppose thefirst substrate121, and includes a common electrode including a transparent conductive material, and a color filter. The color filter may include red, green and blue color filters. These elements may be disposed on a base substrate within thesecond substrate123.

The liquid crystal layer (not illustrated) is interposed between thefirst substrate121 and thesecond substrate123, and orientations of a material thereof are rearranged by an electric field formed between the pixel electrode and the common electrode. As such, the rearranged liquid crystal layer adjusts a transmittance of a light emitted from the backlight unit and passed through thedisplay panel120, such that the adjusted light passes through the color filter of thedisplay panel120 to display images to the outside of the display device at a viewing side thereof

In addition, a lower polarization plate (not illustrated) may be further disposed on a back surface of thefirst substrate121 and an upper polarization plate (not illustrated) may be further disposed on an upper surface of thesecond substrate123. The upper polarization plate and the lower polarization plate may have a planar area corresponding to a planar area of thedisplay panel120.

The upper polarization plate may transmit therethrough only a specific polarized light among light arriving from the outside, and absorb or block the remaining light. The lower polarization plate may transmit therethrough only a specific polarized light among the light emitted from the backlight unit, and absorb or block the remaining light.

A drivingcircuit board125 may be disposed at a one or more side of thedisplay panel120. The drivingcircuit board125 may apply various control signals and/or a power signal to thedisplay panel120 for driving thedisplay panel120 to display an image.

Thedisplay panel120 and the drivingcircuit board125 may be electrically connected to each other by at least one flexible printed circuit board (“FPCB”)127. TheFPCB127 may be a chip on film (“COF”) or a tape carrier package (“TCP”). The number of theFPCBs127 may vary depending on an overall size and/or driving scheme of thedisplay panel120.

Adriving chip129 may be mounted on theFPCB127. Thedriving chip129 may generate various driving signals for driving thedisplay panel120. Thedriving chip129 may be expressed as a driver integrated circuit (“IC”) or a source IC in which a timing controller and a data driving circuit are integrated into a single chip.

Theintermediate frame130 may support an edge of a back surface of thedisplay panel120, and accommodate therein thelight source member140, thelight guide plate150, thereflection sheet160, or the like.

Theintermediate frame130 may have an overall polygonal frame shape with an empty (receiving) space defined therein. In an exemplary embodiment, for example, theintermediate frame130 may have a quadrangular frame shape with an empty (receiving) space defined therein. Theintermediate frame130 may be disposed or formed into a single indivisible shape, or may include a plurality of separate frame portions assembled with each other. Theintermediate frame130 may include a flexible material such as plastic. Theintermediate frame130 may be an injection-molded member such as formed through an injection molding process, for example.

Thelight source member140 includes alight source141 and alight source substrate143 on which thelight source141 is disposed. Thelight source141 may be provided in plural on thelight source substrate143.

Thelight source141 may be disposed at a corner portion or at a side surface of thelight guide plate150. That is, thelight source141 may generates and emit a light toward the corner portion or the side surface of thelight guide plate150. Thelight source141 may include at least one light emitting diode (“LED”) chip (not illustrated) and a package (not illustrated) which accommodates the LED chip therein. In an exemplary embodiment, for example, the LED chip (not illustrated) may be a gallium nitride (GaN)-based LED chip which generates and/or emits a blue light.

The number of thelight sources141 may vary in consideration of the overall size, luminance uniformity, or the like of thedisplay panel120. Thelight source substrate143 may be a printed circuit board (“PCB”) or a metal printed circuit board (“metal PCB”).

Thelight source member140 may be disposed at one side surface, at opposite side surfaces, or at all side surfaces of thelight guide plate150 in consideration of the overall size, luminance uniformity, or the like of thedisplay panel120. That is, thelight source member140 may be minimally disposed at corner portions of thelight guide plate150. Herein, thelight source member140 is assumed to be disposed at a side surface of thelight guide plate150.

Although not illustrated inFIG. 1, a wavelength conversion portion (not illustrated) may be disposed between thelight source member140 and thelight guide plate150. The wavelength conversion portion (not illustrated) may include a material that converts a wavelength of the light. In an exemplary embodiment, for example, the wavelength conversion portion may convert a wavelength of a blue light emitted from a blue LED light source into a white light.

Thelight guide plate150 receives the light from thelight source141 and provides the light to thedisplay panel120. Although described as a plate such as having a relatively large cross-sectional thickness for ease of description for convenience of explanation, thelight guide plate150 may be in the form of a sheet or a film for which the cross-sectional thickness is smaller than that of the plate and is relatively small as compared to the planar size thereof, to reduce an overall thickness of the display device. That is, thelight guide plate150 may be understood as having concepts of a plate and a film for guiding light.

lower surfaces

150aand150bto each other.

In addition, for ease of descriptions, a direction perpendicular to thelight incident surface150cis defined as a first direction D1, a length direction in which thelight incident surface150cextends is defined as a second direction D2 which crosses the first direction D1, and a thickness direction of thelight guide plate150 is defined along a third direction D3. The display device and components thereof may be disposed in a plane defined by the first and second directions D1 and D2. A thickness of the display device and components thereof is taken along the third direction D3.

Thelight guide plate150 according to an exemplary embodiment may include abody portion151 and alens pattern152 provided in plurality on thebody portion151. Thebody portion151 may be considered as common to each of thelens patterns152, where thelens patterns152 each extend from thebody portion151.

Thebody portion151 may include a material having light transmitting characteristics, such as an acrylic resin, e.g., polymethylmethacrylate (“PMMA”), polycarbonate, or a tempered glass, so as to guide the light efficiently.

The plurality oflens patterns152 disposed on thebody portion151 may include a relatively hard coating such as resin, and the resin may be ultraviolet (“UV”) cured to have properties similar to those of polycarbonate. The resin may include an oligomer, a monomer, a photoinitiator, silicone, or the like, and may be classified into a relatively soft resin and a relatively hard resin depending on a content of the silicon and monomer within the resin.

Descriptions of the shape of the plurality oflens patterns152 disposed on thebody portion151 will be described in detail below.

Thereflection sheet160 may include, for example, polyethylene terephthalate (“PET”), and have reflecting characteristics. A surface of a main body of thereflective sheet160 may be coated with a diffusion layer including, for example, titanium dioxide to have a reflecting characteristic. In addition, a main body of thereflection sheet160 may include a material including a metal such as silver (Ag) to have a reflecting characteristic.

Thelower frame170 may include a metal material having relatively high rigidity and excellent heat dissipation characteristics. In an exemplary embodiment, for example, thelower frame170 may include at least one selected from stainless steel, aluminum, an aluminum alloy, magnesium, a magnesium alloy, copper, a copper alloy, and an electrogalvanized steel sheet.

FIG. 2 is a perspective view illustrating an exemplary embodiment of a light guide plate and a light source member of a display device according to the invention, andFIG. 3 is an enlarged perspective view illustrating area “A” ofFIG. 2. In detail,FIGS. 2 and 3 are perspective views respectively illustrating theupper surface150aand thelight incident surface150cof thelight guide plate150 according to an exemplary embodiment.

Referring toFIGS. 2 and 3, thelight guide plate150 according to an exemplary embodiment may include thelens pattern152 disposed on or at theupper surface150a.Thelens pattern152 may be provided in plurality to include a plurality of lenses each lengthwise extending in the first direction D1 and arranged along the second direction D2. A width of thelens pattern152 is defined in a direction perpendicular to the length direction thereof, e.g., a width direction in the second direction D2. In an alternative exemplary embodiment, thelens pattern152 may be provided in plurality to include a plurality of lenses lengthwise extending in the second direction D2 and arranged along the first direction D1.

Eachlens pattern152 may have a semicircular or semi-elliptical cross-section, but exemplary embodiments are not limited thereto. Eachlens pattern152 may have a circular or triangular cross-section, and respective cross-sectional areas of the plurality of lenses may be different from each other.

AlthoughFIGS. 2 and 3 show that thelens patterns152 disposed adjacent to each other in the second direction D2 are arranged successively (e.g., no space therebetween along the second direction D2), exemplary embodiments are not limited thereto. The plurality oflens patterns152 may be spaced apart from each other by a predetermined distance in the second direction D2.

Thelens pattern152 at an upper surface of thebody portion151 may define a portion or an entirety of theupper surface150aof thelight guide plate150. In an exemplary embodiment, theupper surface150aof thelight guide plate150 may be defined byonly lens patterns152, such that the upper surface of thebody portion151 does not define a portion of the overallupper surface150a.Where thelens patterns152 are spaced apart from each other, a portion of a surface of the body portion151 (e.g., a flat surface or the upper surface thereof) may define a portion of theupper surface150aof thelight guide plate150, while thelens patterns152 define another portion of theupper surface150a.However, the invention is not limited thereto.

Thelight guide plate150 according to one or more exemplary embodiment may include thelens pattern152 at theupper surface150athereof to collimate the light emitted through and/or from thelight guide plate150, such that thelight guide plate150 having thelens patterns152 at theupper surface150athereof being viewable from outside the display device may be substantially prevented.

FIG. 4 is a perspective view illustrating another exemplary embodiment of a light guide plate and a light source member according to the invention,FIG. 5 is an enlarged perspective view illustrating area “B” ofFIG. 4,FIG. 6 is a partial enlarged view illustrating area “C” ofFIG. 5, andFIG. 7 is a cross-sectional view taken along line I-I′ ofFIG. 6.FIGS. 4 and 5 are perspective views illustrating thelower surface150band thelight incident surface150cof thelight guide plate150 according to an exemplary embodiment.

Referring toFIGS. 4, 5 and 6, thelight guide plate150 according to an exemplary embodiment includes aprism pattern area500 provided in plural at thelower surface150band alinear pattern area510 which is between adjacentprism pattern areas500.

In addition, thelight guide plate150 includes aprism pattern153 at theprism pattern area500 and alinear pattern154 at thelinear pattern area510. Thebody portion151 may be considered as common to each of theprism pattern153 and thelinear pattern154, as each extend from thebody portion151.

Asingle prism pattern153 includes a plurality of

prisms

153aand153barranged along the first direction D1 which is perpendicular to thelight incident surface150c.

Plural prisms patterns

153 are arranged along the second direction D2 which is parallel to thelight incident surface150c.That is, the plurality of

prisms

153aand153bwhich define a plurality ofprism patterns153 are arranged along both the first and second directions D1 and D2. A collection of the plurality of

prisms

153aand153bare disposed at the collectiveprism pattern area500 and serve to reflect light incident to the plurality of

prisms

153aand153bfrom thelight source141 and to emit the light perpendicularly with respect to a light exit surface of thelight guide plate150 and thedisplay panel120.

A singlelinear pattern154 includes a plurality oflinear patterns154carranged along the second direction D2 parallel to thelight incident surface150c.Plurallinear patterns154 are arranged along the second direction D2. In an exemplary embodiment, alinear pattern154 is disposed adjacent to side surfaces of thelight guide plate150, such as at outer edges thereof in the second direction D2, such that thelinear pattern area510 is an outermost area of thelower surface150balong the second direction D2. A collection of the plurality oflinear patterns154care disposed at the collectivelinear pattern area510 and serve to reflect light refracted by the plurality of

prisms

153aand153band leaked toward a side surface of thelight guide plate150 to be emitted perpendicularly with respect to a light exit surface of thelight guide plate150 and thedisplay panel120. In addition, the plurality oflinear patterns154cmay be disposed at thelinear pattern area510 and serve to reflect light incident to the plurality oflinear patterns154cfrom thelight source141 and to emit the light perpendicularly with respect to a light exit surface of thelight guide plate150 and thedisplay panel120. The LCD device according to one or more exemplary embodiment may improve luminance, illuminance, and luminous efficiency by improving the side leakage of light with thelinear pattern area510.

The plurality oflinear patterns154cat thelinear pattern area510 may have various positions, quantities, lengths, angles and shapes. The details of the shape of the plurality oflinear patterns154cwill be described below.

Thelinear patterns154cmay define a portion of thelower surface150bof the overalllight guide plate150, much like thelens pattern152 may define a portion of or an entirety of theupper surface150aof thelight guide plate150, without being limited thereto. A portion of the lower surface of thebody portion151 may also define a portion of thelower surface150bof thelight guide plate150, along with theprisms153athrough153band thelinear patterns154c. The portion of thelower surface150bdefined by thebody portion151 may be a flat portion at which noprism153athrough153borlinear pattern154cis defined embossed or engraved.

Referring toFIGS. 4 and 5, each of the

prisms

153aand153bmay have a length extending in the second direction D2 parallel to thelight incident surface150cand each of thelinear patterns154cmay have a length extending in the first direction D1 perpendicular to the first direction D1.

The plurality of

prisms

153aand153barranged along the first direction D1 within a singleprism pattern area500 may have lengths in a range from about 5 micrometers (μm) to about 300 μm.

A length of the plurality of

prisms

153aand153barranged along the first direction D1 within a singleprims pattern area500 may gradually increase in a direction from thelight incident surface150ctoward thelight opposing surface150d.That is, a length l₁of theprism153adisposed most adjacent to thelight incident surface150cmay be the smallest, and a length l₂of theprism153bdisposed most adjacent to thelight opposing surface150dmay be the largest. By arranging the plurality of

prisms

153aand153bto have increasing lengths in a direction from thelight incident surface150cto thelight opposing surface150d,a light emitted from thelight guide plate150 may be uniformly provided to thedisplay panel120.

In detail, the light provided from thelight source member140 becomes weaker as a distance from thelight incident surface150cincreases, e.g., toward thelight opposing surface150d.Accordingly, in order to uniformly supply the light to thedisplay panel120, an amount of light reflected through theprism153adisposed closest to thelight incident surface150cshould be reduced, and an amount of light reflected through theprism153adisposed closest to thelight opposing surface150dshould be increased. According to one or more exemplary embodiment, as theprism153adisposed closest to thelight incident surface150chas the smallest length within a singleprims pattern area500 and the lengths of the prisms increase in a direction toward thelight opposing surface150d,light may be uniformly provided to thedisplay panel120 from thelight guide plate150.

Since the lengths of the prisms disposed close to thelight incident surface150care relatively small, in order to secure the uniformity, while the length of thelight source141 is relatively large, a large amount of side leakage light may be generated at a light incident portion of thelight guide plate150. That is, a portion of light incident to the plurality of

prisms

153aand153bfrom thelight source141 may be refracted and leaked to the side surface of thelight guide plate150, without being reflected by the plurality of

prisms

153aand153band emitted perpendicularly as described above.

In addition, a portion of the light emitted from thelight source141 may not be incident to the plurality of

prisms

153aand153bbut may be incident to an area where the plurality of

prisms

153aand153bare absent, thus failing to be emitted perpendicularly from thelight guide plate150 as described above. Accordingly, in one or more exemplary embodiment, in order to re-emit the side leakage light perpendicularly, thelinear pattern154 is disposed at thelinear pattern area510, in addition to disposing theprism pattern153 at theprism pattern area500, thereby improving the side leakage light and increasing the luminance, the illuminance and the luminous efficiency of the backlight unit and the display device.

The

prisms

153aand153barranged along the second direction D2 which is parallel to thelight incident surface150cmay have a predetermined pitch P1. The pitch P1 may be defined as a distance between a center of

prisms

153aand153barranged in a line along the second direction D2 (e.g., within a single first prism pattern area500) and a center of

prisms

153aand153barranged in another adjacent line along the second direction D2 (e.g., within a single second prism pattern area500) may be in a range from about 350 μm to about 400 μm.

Referring toFIGS. 6 and 7, eachprism153cdisposed at theprism pattern area500, as representing theprisms153athrough153binFIG. 4 andFIG. 5, may be formed in a depressed engraved shape or an embossed shape, and may have a semicircular, semi-elliptical, circular or triangular cross-sectional shape. As being depressed, theprism153cmay extend into thebody portion151 from a lower surface thereof. As being embossed, theprism153 may be protruded from thebody portion151 from the lower surface thereof, as shown inFIG. 7. Theprisms153cmay define a portion of thelower surface150bof the overalllight guide plate150, much like thelens pattern152 may define a portion of or an entirety of theupper surface150aof thelight guide plate150, without being limited thereto.

Each of theprisms153cmay have a predetermined width W1 in the first direction D1.

In an exemplary embodiment, for example, each of theprisms153cmay have a width W1 in a range from about 15 μm to about 25 um in the first direction D1.

Theprisms153carranged along the first direction D1 which is perpendicular to thelight incident surface150cmay be parallel to and adjacent to each other, but exemplary embodiments are not limited thereto. Theprisms153carranged along the first direction D1 may be spaced apart from each other by a predetermined pitch. When theprisms153carranged along the first direction D1 are spaced apart from each other by a predetermined pitch, the pitches between adjacent ones of theprisms153carranged along the first direction D1 may be substantially equal to each other or may decrease in a direction from thelight incident surface150ctoward thelight opposing surface150d.

Firstinclined surfaces153c′ of therespective prisms153cmay be parallel to each other, and an angle θ1 between the firstinclined surface153c′ of eachprism153cand a plane common to each of theprisms153cat thelower surface150bof thelight guide plate150 may be in a range from about 45 degrees to about 55 degrees. The common plane may be a lower surface of thebody portion151, without being limited thereto. Alternatively, the firstinclined surfaces153c′ of therespective prisms153cmay not be parallel to each other. That is, theprisms153cmay each have the firstinclined surfaces153c′ having irregular shapes.

Secondinclined surfaces153c″ of therespective prisms153cmay be parallel to each other, and an angle θ2 between the secondinclined surface153c″ of eachprism153cand the plane common to each of theprism153cat thelower surface150bof thelight guide plate150 may be in a range from about 45 degrees to about 55 degrees. Alternatively, the secondinclined surfaces153c″ of therespective prisms153cmay not be parallel to each other. That is, theprisms153cmay each have the secondinclined surfaces153c″ having irregular shapes.

The angle θ1 between the firstinclined surface153c′ of eachprism153cand the plane common to each of theprism153cat thelower surface150bof thelight guide plate150 may be substantially equal to the angle θ2 between the secondinclined surface153c″ of eachprism153cand the plane common to each of theprism153cat thelower surface150bof thelight guide plate150.

A vertex at which the firstinclined surface153c′ and the secondinclined surface153c″ of eachprism153cmeet may have a radius of curvature without being limited thereto.

FIGS. 8a, 8b,9,10,11,12 and13 are perspective views illustrating exemplary embodiment of shapes of the plurality of prisms and the plurality of linear patterns of the light guide plate according to the invention. For convenience of illustration, the opposing side surfaces of thelight guide plate150 along the first direction D1 inFIGS. 8a, 8b,9,10,11,12 and13, may be thelight incident surface150cand thelight opposing surface150ddisposed in order along the first direction D1, without being limited thereto. However, the opposing side surfaces of thelight guide plate150 along the second direction D2 inFIGS. 8a, 8b,9,10,11,12 and13 may not be the end surfaces of thebody portion151. That is, in exemplary embodiments, thelinear pattern area510 may be the outermost pattern area of thelower surface150balong the second direction D2, without being limited thereto.

InFIGS. 8a, 8b,9,10,11,12 and13, although the plurality of prisms and the plurality of linear patterns of the light guide plate are depicted as having a triangular cross-section, the invention is not limited thereto. The plurality of prisms and the plurality of linear patterns may have a semicircular, semi-elliptical, or circular cross-sectional shape in various exemplary embodiments. In addition, the plurality of prisms of the light guide plate may have an embossed shape as inFIGS. 8a, 8b,9,10,11, and13, or may have a depressed engraved shape as inFIG. 12.FIG. 8bindicates prisms and linear patterns at a lower surface of thelight guide plate150 viewed from an upper surface of the light guide plate ofFIG. 8a.

Referring toFIGS. 8aand 8b, each of thelinear patterns154chas a length extending in the first direction D1 which is perpendicular to thelight incident surface150c.Lengths of thelinear patterns154cmay increase as a distance along the second direction D2 to a center portion of thelinear pattern area510 decreases.

Each of thelinear patterns154cmay have a predetermined width W2 in the second direction D2 which is parallel to thelight incident surface150c.In an exemplary embodiment, for example, each of thelinear patterns154cmay have a width W2 in a range from about 5 μm to about 500 μm in the second direction D2. When the width W2 of thelinear pattern154cis less than about 5 μm, an effect of perpendicularly re-emitting the light leaked toward the side surface of thelight guide plate150 may be difficult to achieve. On the other hand, when the width W2 of thelinear pattern154cis more than about 500 μm, the patterns of thelight guide plate150 may be visually recognized on thedisplay panel120.

An angle θ3 between the firstinclined surface154c′ of eachlinear pattern154cand a plane common to each of thelinear patterns154cat thelower surface150bof thelight guide plate150 may be in a range from about 1 degree to about 80 degrees. As shown inFIGS. 8aand 8b, each of theprisms153cand thelinear patterns154cextends from a common surface as the lower surface of thebody portion151 which is flat. Together, theprisms153c,thelinear patterns154cand the (flat) lower surface of thebody portion151 define an entirety of thelower surface150bof thelight guide plate150.

Referring toFIGS. 8a, 8band9, each of thelinear patterns154cmay have a depressed engraved shape or an embossed shape.FIGS. 8aand 8bshow thelinear patterns154chaving an engraved shape (e.g., recessed from the lower surface of the body portion151) while theprisms153chave an embossed shape (e.g., protruded from the lower surface of the body portion151). For a same arrangement as illustrated inFIGS. 8aand 8b,FIG. 9 shows each of thelinear patterns154cand theprisms153chaving an embossed shape (e.g., protruded from the lower surface of the body portion151).

Referring toFIGS. 9 and 10, each of thelinear patterns154cmay have a triangular (FIG. 9) or semicircular (FIG. 10) cross-sectional shape, but exemplary embodiments are not limited thereto. Each of thelinear patterns154cmay have a semi-elliptical, circular or trapezoidal cross-sectional shape.

Referring toFIGS. 9 and 11, the plurality oflinear patterns154cmay be adjacent to and parallel to each other (FIG. 9), or may be spaced apart from each other by a predetermined pitch (FIG. 11). In addition, the plurality oflinear patterns154cwithin a singlelinear pattern154 at thelinear pattern area510 may each have a substantially equal length as each other (FIG. 11) or may have different lengths from each other (FIG. 9).

Referring toFIGS. 11 and 12, each of thelinear patterns154cstarts from thelight incident surface150c(FIG. 11) and extends toward thelight opposing surface150d,or starts from thelight opposing surface150d(FIG. 12) and extends toward thelight incident surface150c.That is, ends of thelinear patterns154cmay be coplanar or aligned with a side surface (150cor150d) of thelight guide plate150, or may be coplanar or aligned with both of opposing side surfaces (150cand150d) of thelight guide plate150. Where first ends of thelinear patterns154cmay be aligned with a particular side surface (150cor150d) of thelight guide plate150, second ends of thelinear patterns154copposite to the first ends thereof may be spaced apart from the opposing side surface (150dor150d) along the first direction D1.

Referring toFIG. 13, the plurality oflinear patterns154cmay be spaced apart from each other in an alternate manner. As being disposed in an alternate manner, a first linear pattern forms a first angle with respect to thelight incident surface150cof thelight guide plate150, and a second linear pattern adjacent to the first linear pattern forms a second angle with respect to thelight incident surface150cof thelight guide plate150 which is different from the first angle. The first linear pattern forming the first angle alternates in the second direction with the second linear pattern forming the second angle. In an exemplary embodiment, for example, the plurality oflinear patterns154cmay be arranged at an angle in a range from about 0 degrees to about 60 degrees with respect to each other instead of being parallel to each other.

As set forth hereinabove, the backlight unit and the display device according to one or more exemplary embodiments may have high luminous efficiency by improving light incident to the light guide plate from the light source that leaks toward a side surface without being emitted perpendicularly.

The backlight unit and the display device according to one or more exemplary embodiments may achieve a slimmer display device and reduce manufacturing costs by omitting an optical sheet.

While the invention has been illustrated and described with reference to the exemplary embodiments thereof, it will be apparent to those of ordinary skill in the art that various changes in form and detail may be formed thereto without departing from the spirit and scope of the invention.

Claims

What is claimed is:

1. A backlight unit comprising:

a light source which generates light used by a display panel to display an image; and

a light guide plate which guides the light from the light source towards the display panel, the light guide plate comprising:

an upper surface facing the display panel,

a lower surface opposing the upper surface, comprising:

a prism pattern area provided in plurality, and

a linear pattern area provided between prism pattern areas, and

a light incident surface facing the light source,

wherein

the prism pattern area comprises a prism provided in plurality arranged along a first direction perpendicular to the light incident surface,

the linear pattern area comprises a linear pattern provided in plurality arranged along a second direction parallel to the light incident surface, and

within the prism pattern area,

a length of each of the prisms extends in the second direction parallel to the light incident surface, and

lengths of the prisms increase as a distance along the first direction from the light incident surface increases.

2. The backlight unit ofclaim 1, wherein within the linear pattern area between prism pattern areas, each of the linear patterns has at least one of triangular, semicircular, semi-elliptical, circular and trapezoidal cross-sectional shape.

3. The backlight unit ofclaim 1, wherein

the light guide plate further comprises a body portion having a lower surface common to each of the prisms and the linear patterns, and

within the linear pattern area between prism pattern areas, each of the linear patterns has at least one of an embossed shape protruded from the lower surface of the body portion and a depressed engraved shape recessed from the lower surface of the body portion.

4. The backlight unit ofclaim 1, wherein for each of the plurality of linear patterns within the linear pattern area between prism pattern areas:

a length thereof extends in the first direction perpendicular to the light incident surface and a width thereof extends in the second direction parallel to the light incident surface, and

the width of each of the linear patterns is in a range from about 5 micrometers to about 500 micrometers.

5. The backlight unit ofclaim 1, wherein

within the linear pattern area between prism pattern areas, in cross-section, each of the plurality of linear patterns includes a first inclined surface which forms an angle in a range from about 1 degree to about 80 degrees with respect to the lower surface of the body portion.

6. The backlight unit ofclaim 1, wherein within the linear pattern area between prism pattern areas, the plurality of linear patterns are disposed directly adjacent to each other along the second direction and parallel to each other.

7. The backlight unit ofclaim 1, wherein within the linear pattern area between prism pattern areas, the plurality of linear patterns are spaced apart from each other along the second direction.

8. The backlight unit ofclaim 1, wherein in a plane defined by the first and second directions, within the linear pattern area between prism pattern areas, linear patterns adjacent to each other are arranged at an angle in a range from about 0 degrees to about 60 degrees with respect to each other.

9. The backlight unit ofclaim 1, wherein within the linear pattern area between prism pattern areas, a length of each the plurality of linear patterns extends in the first direction perpendicular to the light incident surface.

10. The backlight unit ofclaim 1, wherein within the linear pattern area between prism pattern areas, the linear patterns have lengths equal to each other.

11. The backlight unit ofclaim 1, wherein within the linear pattern area between prism pattern areas, the linear patterns have different lengths from each other.

12. The backlight unit ofclaim 1, wherein within the linear pattern area between prism pattern areas, lengths of the plurality of linear patterns increase as a distance from a center portion of the linear pattern area along the second direction decreases.

13. The backlight unit ofclaim 1, wherein within the linear pattern area between prism pattern areas,

a length of each the plurality of linear patterns extends in the first direction perpendicular to the light incident surface, and

ends of each of the linear patterns of which the length thereof extends in the first direction is aligned with the light incident surface.

14. The backlight unit ofclaim 1, wherein

the light guide plate further comprises a light opposing surface opposing the light incident surface along the first direction perpendicular to the light incident surface, and

within the linear pattern area between prism pattern areas,

ends of each of the linear patterns portions of which the length thereof extends in the first direction is aligned with the light opposing surface.

15. The backlight unit ofclaim 1, wherein within the prism pattern area, the plurality of prisms are disposed directly adjacent to each other in the second direction and parallel to each other.

16. The backlight unit ofclaim 1, wherein

within the prism pattern area, each of the prisms has at least one of an embossed shape protruded from the lower surface of the body portion and a depressed engraved shape recessed from the lower surface of the body portion.

17. The backlight unit ofclaim 1, wherein

within the prism pattern area, in cross-section, each of the plurality of prisms includes a first inclined surface and a second inclined surface respectively forming an angle with respect to the lower surface of the body portion, the angles within each of the prisms being equal to each other.

18. The backlight unit ofclaim 1, wherein the upper surface of the light guide plate which faces the display panel further comprises a lens pattern provided in plurality.

19. A display device comprising:

a display panel which displays an image with light;

a light source which generates the light; and

an upper surface facing the display panel,

a lower surface opposing the upper surface, comprising:

a prism pattern area provided in plurality, and

a linear pattern area provided between prism pattern areas, and

a light incident surface facing the light source,

wherein

the linear pattern area comprises a linear pattern provided in plurality arranged along a second direction parallel to the light incident surface,

within the prism pattern area,

lengths of each of the prisms increase as a distance along the first direction from the light incident surface increases,

within the linear pattern area between prism pattern areas, the plurality of linear patterns are spaced apart from each other along the second direction, and

within a plane defined by the first and second directions, each of adjacent linear patterns spaced apart from each other is disposed inclined with respect to the light incident surface of the light guide plate.

20. The display device ofclaim 19, wherein within the linear pattern area between prism pattern areas, among the adjacent linear patterns spaced apart from each other,

with respect to the light incident surface of the light guide plate, a first linear pattern forms a first angle and a second linear pattern forms a second angle,

the first linear pattern forming the first angle alternates in the second direction with the second linear pattern forming the second angle, and

the first and second linear patterns form an angle in a range from about 0 degrees to about 60 degrees with respect to each other.